Shifting devices of this type for motor vehicles are already known from the generic DE 198 33 397 A1, and are used for example in automatic transmissions of a planetary and spur gear construction. The shifting devices replace for example conventional lamellar couplings, and this has an advantageous effect on the weight and the required installation space for the motor vehicle transmission.
Further, the cone angle between the conical surfaces and the transmission axis results in a force amplification, in such a way that the shifting force required for the frictional fit is reduced by comparison with the shifting force required in a lamellar coupling.
In other words, in the above-disclosed shifting device, for transmitting comparable torques, fewer friction surfaces are required than in the lamellar couplings conventionally used in automatic transmission, and so the power losses due to drag torques are advantageously reduced.
In particular at high transmission rotational speeds, however, it has been found that the drag torques do not fall off to the expected extent, but still lead to undesirably large power losses in the motor vehicle transmission.
Therefore, the object of the invention is to provide a particularly light and compact shifting device for motor vehicle transmissions, which only has low power losses from drag torques even at high rotational speeds.